Factors affecting arteriovenous fistula maturation in patients with end stage renal disease

Factors affecting arteriovenous fistula maturation in patients with end stage renal disease

Ayman Omar, MD; Nehad Zaid, MD

Vascular Surgical Unit, Department of General Surgery, Menoufiya University Hospitals, Shebin El-Kom, Egypt.

Abstract

Background: Failure of arteriovenous fistula to mature is a devastating problem in patients

requiring  regular  haemodylasis.  Many factors  might  be incriminated  in such dilemma.

Aim: to evaluate different factors that might affect arteriovenous fistula maturation in a prospective study.

Methods: Fifty patients (31 males & 19 females) with end stage renal disease and requiring

regular haemodialysis underwent their suitable fistulas. Successful fistulas were categorized into early matured or delayed one, where by mature fistulas were those matured in  6 weeks. Fistulas' maturation was evaluated in respect to the association of certain risk factors such as gender, age, smoking, diabetes, hypertension, obesity & hepatitis-C virus or the type of fistula selected.

Results: Female gender and the association of diabetes adversely affect the maturation of fistulas. Fistula early maturation was lower in females (28.6 vs 59.1, P<0.05) Also.fistula early maturation was lower in diabetics versus non-diabetics (28.6 vs.63.6, P<0.05). Similarly; proximal  fistulas  matured  early  than  distal  one    (71.4  vs   28.6,  P<O.05).

Conclusion: Arteriovenous fistula patency & maturation is worse in women & diabetic

patients. Proximal AVF may be selected as a first choice. Duplex ultrasonography is a useful aid in choosing the proper fistula.

Introduction:

End-stage renal disease (ESRD) and the

need for dialysis remain one of the most challenging problems facing both nephrologists and surgeons. Even with renal replacement therapy, ESRD patients have a signifcantly shorter life expectancy across quartiles of age. Successful construction and maturation of a dialysis fistula are necessary prerequisites for these patients to survive their diminished life span.l

Satisfactory blood  flow  through an arteriovenous fistula (AVF) is   essential for adequate haemodialysisinpatients with ESRD. Three components of a well-functioning fistula included: inflow artery, needle-stick segment and native  outflow vein. All of these components contribute to the maturation and proper functioning of a fistula.2

The most frequent problems with fistulas are weak flow after construction. Failure of a fistula to mature can usually be anticipated

within 1 month following its creation. However; the National  Kidney  Foundation Dialysis Outcomes Quality Initiative guidelines3 consider the fistula non-mature after 4 months of its creation if it does not satisfy  the requirements for  regular haemodyalsis.

Preoperative non-invasive assessment by duplex sonography is very helpful in locating veins that are not clinically visible and also provides information about the functional characteristics of veins, including  venous outfow. Duplex sonography is the method of choice  for evaluation of arteries (wall, haemodynamics  &  calcification).4

The aim of the present study is to evaluate different factors that might affect AVF maturation in a sample of Egyptian patients with end stage renal disease.

Patients and methods:

Fifty patients with ESRD on regular haemodialysis or  preparing for  regular

haemodialysis were  included in the study. Patients included in the study were essentially recruited from the vascular out-patient clinic at Menou:fia University Hospitals, Shebin El­ Kom, or directly referred from the Department ofNephrology. The study was conducted over

12 months duration staring from first of March

2010.

Inclusion criteria:  All patients 18 years old  of either  gender  with  ESRD  requiring maintenance haemodiaysis, first time to do A­ V fistula  in upper limb were included into the study.

Exclusion criteria: Patients with peripheral vascular  disease  in the target  limb, patients with current  cardiac  problem  affecting the fistula flow (ejection fraction <40%), patients with  known outflow venous obstruction (thrombosis, cervical rib, ... etc), patients with vascular  malformation in the target limb & patients with ESRD requiring synthetic grafts.

Patients' assessment:

Pre-operative assessment:

All the patients underwent  full history & clinical  examination. Allen's test was done whenever distal fistula is planned Also; duplex study is made in order to select a suitable artery with its suitable superficial vein.Furthermore; vein distensability was checked using proximal compression  by    the  application  of sphygmomanometer cuff.  We  intended to choose the artery and vein minimum diameters (mm for the artery and   2.5 mm for the vein).

Incorporation of the clinical assessment & duplex findings was made by independent consultant vascular surgeon in selecting fistula of choice for every patient. The necessary preoperative  precautions  & tests were made e.g. controlling systemic blood pressure, .. ect.

Intra-operative evaluation:

The  intra-operative evaluation was essentially based on assessing the condition of the selected  vessels compared to the finding expected  by clinical  and duplex  evaluation.

Post-operative evaluation &  care:

Immediate postoperative evaluation of the patency of fistula was made either by palpating a thrill along the course of the outflow vein,

auscultating machinery murmur whenever the outflow  vein  is impalpable and/or  Doppler examination especially in  obese  patients.

All patients were followed up weekly for

16 weeks post-operatively for patency or arise of complications. Duplex  examination was performed at4, 6 & 16 weeks post-operatively measuring blood  flow  & diameter of  the outflow vein. At the  first session of haemodialysis; the adequacy of the flow in the fistula was reported.

Results:

Patients' demography:

Fifty  patients (31 males  & 19 females)

participated in  the  study. Mean  age  was

49.96±15.63 varying  from  19-80  years.  19 patients were smokers. 21 were diabetics (Type II). 41 have systemic hypertension & 26 were hepatitis C +ve.The dominant right upper limb was in 44 patients.

The  majority of patients 43/50  showed

fistula maturation. Complications were arisen in 7 patients; thrombosis in 3 patients, infection in one patient, haematoma and fistula disruption in 2 patients, and one has died. The successful fsitulas comprised 25  proximal (brachio­ cephalic) & 18 distal  (radio-cephalic) one.

Consequently; patients who showed fistula maturation were divided into two groups. First group included patients in whom fistulas have been  matured in 6 weeks.  Second group included patients in whom fistulas have been matured in > 6 weeks. Statistical significance was made  to classify fistula  maturation in regards to that interval (6 weeks).

Risk factors that  might  affect fistula

maturation:

Several factors were looked for its relationship with fistula maturation including:Gender, age, smoking,  diabetes,  hypertension, obesity  & hepatitis-C virus. The association of all these factors  was evaluated in its relationship to either early matured fistula or the delayed matured one. It was obvious that the female gender  and the association of diabetes were the only  significant factors that may be associated with  delay in fistula  maturation. These  factors are  presented by  Table(l).

Table (1): Risk factors that might affect fistula maturation.

Typeof fistula in relation to fistula maturation: Proximal fistula matures earlier than distal one. This may be due to high blood flow in

proximal fistula that helped earlier maturation. This difference  was presented  by Table(2).

Table (2): Relationship between type ofjistula andfr.stula maturation.

Discussion:

Non-maturation of native  arteriovenous fistula for hemodialysis still is problematic in a large group of patients. The mechanisms of maturation and factors responsible for non­ maturation are poorly understood as evidenced by high  non-maturation rates  up to 30%.5

There  is marked variation in literature regarding the definition of a "successful"fistula. The defmition has included the presence of a thrill or bruitability to use the fistula for at least one dialysis sessioor ability to use the fistula reproducibly for dialysis for at least one month with a dialysis blood flow 350 ml/min.6

The   problem  of  fisula  patency  and maturation is distorted between lots of variants. Health service;  whether Nephrologist' care, Vascular Surgeon' judgment and  dialysis Nursecannulation may have a role in timing, selection & successfulness of the AVF. Also; patients' agegender and associated co-morbid risk factors can influence the outcome of fistula creation.?

In regards to age, the progressive increase in  age  of  patients undergoing regular hemodialysis is responsible for the growing number of  AVF complications & failure. Patients over  65  years  old  have  a higher incidence of co-morbid factors  as diabetes mellitus, atherosclerosis, neoplasms, and heart failure. Also; vascular  changes  (due to age atherosclerosis, vascular calcifications, stiffuess of vessels)  can make difficult creation  and delayed  maturation  of   the    AVF.8,9

In our studythe advancement  of age was

not  a significant factor  influencing fistula maturation. This  came  in agreement with previous reports ofWolowczyk et al, 2000 to

& Ridao-Cano, et a12002.11

Patient gender does seems to influence fistula maturation world-wide. The patency of distal  forearm, wrist  or snuffbox AVFs  is poorer in women than in men.12,13 Since, this seems to apply also to more proximal AVFs

it may be unrelated to the larger vessels of men and may have a hormonal basis.lO Also possible explanation is that vessels are of smaller caliber in women than in men, and therefore less likely to dilate sufficiently thereby contributing to a

30% lower  maturation rate.l4,15 In our study

also females exhibited a lower maturation rates than males.

In diabetic patients; little attention has been paid in literature to the special and demanding problem  of   vascular access. There is controversy regarding the influence of diabetes on fistula patency & maturation. Some authors claimed that  diabetes has  adverse effect on fistula flow  rate  and  patency;16,13  whereas others have found no effect.l7,18 In our study we  have found that diabetes mellitus significantly delayed fistula maturation and proximal (arm) fistula  is preferred in diabetic patients.

Obesity does  seem to  influence fistula maturation in other way because deeper veins are more  difficult to cannulate, although this does not affect patency.19,16 Inour study; we did  not  find  a relationship between fistula maturation and obesity but this may be due to little discrepancy in weight among the studied group.

Similar irrelevant relationship between fistula maturation and smoking, hypertension or hepatitis-C virus was  observed in our patients.

Vessel size seems to be an important factor affecting fistula maturation.  Small arteries and veins have higher initial failure rates, more frequent failure to mature and poorer long term patency. It has been  suggested that a cut-off of  2 mm  for  both  the  arterial and  venous diameters should be used.20,21 Fortunately; we found that  as  long  as  the  artery and  vein minimum diameters (2 mm for  the  artery and2.5 mm  for  the  vein); there  was  no correlation between vessel diameter and likelihood of fistula  maturation.

Access position is a matter of wise judgment. More  proximal AV  fistulae have improved blood flow and patency but left fewer options for access in the event  of failure.16,13 In our study; we encountered early maturation of proximal fistula than distal one.

Finally; the preoperative vein mapping is very important in this regard as it allows  one to choose the best  vein  the  first time  rather than the traditional approach that places a high value on starting the quest in the non-dominant arm, in the most distal available vein, reserving other sites for subsequent remedial operations. Preoperative ultrasound vein mapping should be the principal guide  to which  arm  and  to which  vein  to use,  with  the  intent being  to perform the best operation the first time using the best vein.13

In  conclusion; primary access is  best provided by a distal  autogenous AVF  in the non-dominant (whenever possible) arm. Proximal AVF  may  be required in patients with poor veins or patients with diabetes. Fistula patency  and maturation is worse in women  & diabetics. Preoperative duplex scanning facilitates proper choosing.

References:

1- Niren A, Ankur C: The two-stage brachial artery-brachial vein autogenous fistula for hemodialysis: An alternative autogenous option for hemodialysis access.JVasc Surg

2005; 42: 806-810.

2- Shenoy S: Creative surgical solutions for creating and revising AV  shunts. J Vasc Ace 2006; 7: 199-201.

3- NKF-DOQI clinical practice guidelines for vascular access: National Kidney Foundation-Dialysis Outcomes Quality Initiative. Am J Kidney Dis 1997;  30(3):

150-191.

4- Marko Malovrh: The role of sonography in the planning of arteriovenous fistulas for hemodialysis. Seminars in Dialysis 2003;

16(4): 299-303.

5-  Allon  M,   Robbin ML: Increasing

arteriovenous fistulas in  hemodialysis patients: Problems and solutions. Kidney Int 2002;  62(4): 1109-1124.

6- NKF-DOQI clinical practice guidelines for vascular access: Guideline 29: Goals of access placement: Maximizing  primary A­ V fistulae. Am J Kidney Dis 2001;  37(1):

169.

7- Feldman HI, Joffe M, Rosas SE, Burns JE, Knauss J, Brayman K: Predictors of successful arteriovenous fistula maturation.